Rotary drilling head assembly

ABSTRACT

A rotary drilling head assembly for wellbore forming operations comprising a stationary housing which supports a rotatable sleeve. A stripper rubber located within the rotatable sleeve slidably receives a tubing string in sealed relationship therethrough. A second stripper rubber is removably mounted in spaced superimposed relationship above the first rubber, with the first rubber being larger than the second so as to enable different size tubular goods to be withdrawn from the borehole with one of the strippers always sealingly engaging a marginal length of the tubular goods. Accordingly, the apparatus provides a method of controlling the well pressure during borehole forming operations. Each of the strippers are removably affixed to the rotating sleeve by a quick disconnect means in the form of a circumferentially extending hinged clamp means.

[ Mar. 4, 1975 Primanv Eraminew-Samuel Scott AssistantE.\'amine/'Randall Heald Attorney, Agent, or Firm-Marcus L. Bates [57]ABSTRACT A rotary drilling head assembly for wellbore forming operationscomprising a stationary housing which supports a rotatable sleeve. Astripper rubber located within the rotatable sleeve slidably receives atubing string in sealed relationship therethtough. A second stripperrubber is removably mounted in spaced superimposed relationship abovethe first rubber, with the first rubber being larger than the second soas to enable different size tubular goods to be withdrawn from theborehole with one of the strippers always sealingly engaging a marginallength ROTARY DRILLING HEAD ASSEMBLY Inventor: Morris S. Biffle, 105Cielo Vista,

Odessa, Tex. 79761 Filed: Mar. 8, 1973 Appl. No.: 339,037

US. 64/235, 166/82, 175/84, 403/338, 285/10, 277/31 lnt. Fl6d 3/06 Fieldof Search..i........ 64/235; 166/82, 83, 84; 175/84; 403/338, 336;285/10, 11, 96, 97, 106, 351, 110, 111; 277/31, 71

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ROTARY DRILLING HEAD ASSEMBLY BACKGROUND OF THE INVENTION Duringborehole forming and borehole repair operations, where substantialbottomhole pressures are encountered, and sometimes in variousoperations associated with the completion of hydrocarbon producingwells, it is necessary to rotate the tool string, tubing string, ordrill pipe string while the string is being lowered into or withdrawnfrom the well bore. This expedient is attained by the provision of arotating seal member, referred to herein and in the prior art as astripper rubber, with the stripper being rotatably positioned near thewell head in sealing relationship respective of the piping going into orout of the borehole.

In order to prevent excessive wear of the stripper, it is necessary thatthe stripper rotate with the piping so that the only significant wearencountered is in the longitudinal movement of the piping relative tothe stripper.

In my prior patent No. 3,724,862 to which reference is made for furtherbackground of the present invention as well as many additional detailsof its operation, there is disclosed a blow-out preventer of therotating type, hereinafter throughout this disclosure referred to as aBOP of the rotating type," or in some instances, merely a RBOP (rotatingblow-out preventer).

Throughout this disclosure, the term tubing string or piping refers to adrill string, including the various tools attached thereto, such as astablizer, a drill collar,-

as well as the kelly, and further includes other tubular goods such asproduction tubing, instrument packages, jars, fishing tools, and thelike. The drill or tool string is generally circular or round inconfiguration, except for the kelly which usually is non-circular inconfiguration. Hence, the stripper must deform sufficiently to sealinglyengage the outer peripheral surface of each of these recited members,

In the various prior art rotary drilling head assemblies; or RBOP, thestripper is usually affixed to a lower marginal portion of the rotatingsleeve, thereby rendering replacement or repair extremely difficult whenthe head is operatively affixed to the upper terminal end of the wellbore.

In my previously referred to issued patent, the rotating stripper isaffixed to the upper terminal end of the rotating sleeve by means of themounting plate bolted onto structure associated with the sleeve.Substitution of one stripper for another must sometime be carried outseveral times each trip the tool string makes into the borehole, andaccordingly, it is desirable to be able to rapidly renew the stripper,or to substitute one size stripper for another. Moreover, it isdesirable to provide a reliable seal means at the interface formedbetween the fixed and rotating sleeves and to protect the bearingsurfaces which rotatably secure the rotating sleeve from up or downholethrust by the provision of improvements in the seal and lubricationsystem therefor. It is also desirable to have provisions by which twodivergent sizes of tubing string can be sealingly run uphole anddownhole through the RBOP without resorting to other means of sealingthe upper annulus between the tool string and the wall of the well bore.

SUMMARY OF THE INVENTION Method and apparatus for sealing the upperannulus formed between a borehole wall and a tool string so as tocontrol the pressure within the upper borehole annulus. The apparatus iscomprised of a RBOP assembly having a seal assemblysupported by astationary housing, with the seal assembly comprising a rotatable sleevemember journaled to a stationary housing, with a stripper beingremovably mounted to the rotatable sleeve member in a new and improvedmanner. The interface between the rotatable sleeve and the housing has aseal therebetween which is protected by a pressurized lubricationsystem.

In one form of the apparatus, spaced axially aligned strippers ofdifferent inside diameters (i.d.s) are removably mounted to the rotatingsleeve so as to enable different sizes of series connected components ofthe tool string to sealingly pass therethrough, with one of thestrippers always sealingly engaging an outermost marginal length of thetool string.

The method of the present invention is carried out by attaching thespaced axially aligned strippers at the upper extremity of the boreholewith the upper stripper being smaller in diameter than the lowerstripper so that the upper stripper normally sealingly engages the outerperipheral wall surface of the tubing string until the tubing stringenlarges in outside diameter (o.d.) to a value which precludes its beingreceived within the small i.d. stripper, whereupon the enlargement ispulled into sealing engagement with the lower and larger stripper, theupper and smaller stripper then is removed from the BOP, therebyenabling the drilling operation to continue with the string beingdisposed in sealing engagement with the larger and lowermost stripper assembly.

Accordingly, a primary object of the present invention is the provisionof improvements in RBOPs which are more efficient in operation, andwhich have longer life due to improved characteristics of wear andsealing.

Another object of the invention is to provide improvements in rotarydrilling heads by the provision of a removable stripper which is held inoperative relationship by a clamp means.

A further object of this invention is to provide improvements in apressure lubrication system for maintaining the seal components of a BOPisolated from foreign debris including drilling mud.

A still further object of this invention is to provide a rotating BOPhaving dual strippers therein which sealingly accommodate different sizecomponents associated with a drill string.

Another and still further object is to provide an improved method ofcontrolling the pressure in the borehole annulus where high bottomholepressures are encountered.

An additional object of this invention is to provide an improved methodof carrying out a drilling operation wherein tubular goods of varyingdiameters must be run into and out of the borehole.

Another object of the invention is to provide a method of going into andcoming out of a borehole with a tool string of varying o.d., wherein theannulus between the tool string and the borehole wall must be sealedagainst fluid flow.

These and various other objects and advantages of the invention willbecome readily apparent to those skilled in the art upon reading thefollowing detailed description and claims and by referring to theaccompanying drawings.

The above objects are attained in accordance with the present inventionby the provision of a combination of elements which are fabricated in amanner substantially as described in the above abstract and summary.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of arotating BOP made in accordance with the present invention;

FIG. 2 is a longitudinal, cross-sectional, side view of the rotating BOPdisclosed in FIG. 1, with some additional parts being included to addclarity to the drawmgs;

FIG. 3 is an enlarged, fragmentary, cross-sectional view of part of theapparatus disclosed in FIGS. 1 and 2, with some parts not being shown insections, and other additional parts being diagrammatically illustrated;

FIG. 4 is a fragmentary, enlarged, cross-sectional view of part of theapparatus disclosed in FIGS. 1 and FIG. 5 is a fragmentary, enlarged,detailed side elevational view of part of a clamp apparatus disclosed inFIGS. 1 and 2;

FIGS. 6-10 are part schematical, part diagrammatical, partcross-sectional, broken side views of apparatus used in carrying out themethod of the present invention; and

FIGS. 11-13 are longitudinal cross-sectional views of apparatus made inaccordance with another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGS. 1 and 2 ofthe drawings, in conjunction with FIGS. 3-5, there is disclosed arotating BOP generally indicated by the arrow at numeral 10. The RBOP iscomprised of a stationary housing 13 which is bottom supported from aflange 11, and which rotatably supports a rotatable sleeve member 12spaced from a fixed sleeve member 12. Outlet flange 14 can be connectedto a mud pit flow line (not shown). Inlet 15 is axially aligned with alarge stripper 16. The stripper is removably affixed to the rotatablesleeve member and moves therewith so that flow from inlet 15 is divertedby the stripper through the outlet 18 and into the mud pit flow line.

Load bearing spaced tapered roller bearings 19 and 20 prevent thrust ofthe stripper assembly uphole or downhole and for this reason thebearings must be able to withstand a load proportional to theanticipated pressures which may be encountered within the boreholeannulus.

A marginal length of the stationary skirt is polished at 22 so as topresent low friction with respect to the illustrated spaced hydraulicseal means. The annular rotating seal backing plate 23 captures the sealtherein as will be described in greater detail later on.

As best illustrated in FIG. 4, the first or larger stripper means isprovided with a circumferentially extend ing outwardly directeddovetailed projection 24 which is compressed into sealing engagementwith a complementary shaped annular circumferentially extending grooveformed between the illustrated component parts.

A series of radially spaced countersunk fastener means 27 are arrangedalong a bolt circle and provide means by which the stripper can beremovably affixed to the rotating skirt. A small removable stripperassembly 29 is affixed to the larger underlying split plate assembly 39by means of radially spaced bolts 30 set in a bolt circle, with bolts 30being radially misaligned with respect to bolts 27. The small stripper34 has a maximum id 35 substantially smaller than the maximum id of thelarge stripper.

The stripper plate assembly 37 compresses the illustrated outwardlydirected flange of the stripper against the split rubber hold down plate39.

A bowl clamp adapter ring assembly 40 is bolted onto the rotating sleevein underlying aligned relationship respective to the outwardly directedshoulder 41 and in spaced relation respective of the outwardly directedshoulder 42 so that the two spaced circumferentially extending outwardlydirected shoulders may be forced towards one another by means of theremovable clamp member, generally illustrated by the arrow at numeral43.

The circumferentially extending inwardly directed groove 44 of the clamphas an innermost wall portion spaced from members 41 and 42 so that theillustrated complementary wedge surfaces 53 and 54 of the stripperrubber and bowl adapter ring are forced into engagement as the splitring and clamp cooperate to force the members 41 and 42 towards oneanother with a tremendous force.

Retainer pin 45 pivotally secures the clamp assembly to the bowl clampring adapter, while hinge pin 46 is spaced outwardly therefrom andhingedly engages link 47 which connects together the two semi-circularhalves of the clamp 48 and 49. Tension bolt 50 engages one of theswingable free ends of the two clamp halves so that the nut thereon canbe torqued thereby bringing the free ends towards one another which inturn forces member 41 towards member 42 due to the wedge surface formedon the split ring and the clamp.

It will be noted that pin 45 connects the two clamp halves to the bowlclamp adapter ring so that the clamp halves can be swung away from oneanother in a pivotal manner about pin 45 when it is desired to removethe split ring and the stripper from the bowl. Lifting eye 52facilitates lifting the entire BOP assembly for installation ortransportation purposes.

Looking now to the lubrication supply system disclosed in FIG. 3, inconjunction with the details of FIG. 2, there is seen a positivedisplacement pump connected to a source of lubrication (not shown)thereby providing a pressurized lub supply at 55'. Conduit 55' isconnected to passageway 56 which in turn communicates with the isolatedchamber within which there is disposed the before mentioned seal of thehydraulic seal assembly.

Inwardly directed polished wall 57 terminates in a circumferentiallyextending upper groove 58, while polish wall 59 is a continuation of thebefore mentioned wash pipe of polished wall 22.

Seal 60 has a lower planer face which sealingly engages the uppershoulder 61 of the stationary sleeve member, with the last namedshoulder being spaced from shoulder 62 of the rotating sleeve member.Seal 63 is a deformed chevron resilient member which sealingly engagesopposed polished wall surfaces 57 and 59. The before mentioned retainerring can be secured to the wash pipe if desired, however, such anexpedient presents an additional wearing surface to the assembly.

Looking now to the details of FIGS. 6 10, there is seen illustratedtherein the before mentioned rotatable sleeve member 12 having spacedaxially aligned strippers 16 and 34 removably mounted therein in amanner similar to that disclosed in FIGS. 1 5. The upper stripper mountassembly 29 includes a bolt circle 30 formed thereon for attachment tothe large stripper mounting means 39, which in turn is affixed to therotating sleeve. A tool string 64 is made up ofjoints of drill pipe, forexample, with the drill pipe having upset tool joints in the form ofboxes and pins providing for the illustrated enlargement 65. The smallstripper is sufficiently resilient to conform to the enlargement 65 aswell as to the nominal drill pipe o.d.

In FIGS. 11-13, the RBOP of the present invention is mounted to theupper extremity of a non-rotating BOP 68. A third and still lowerstripper 69 is mounted to the upper terminal end portion of thenon-rotating BOP in axial alignment with the stripper 16. Outlet 70 isflow connected to ambient, preferably the mud pit, with a valve (notshown) being interposed therein in the usual manner. Numeral 71indicates the upper end of the borehole casing or the upper end of ablind ram. The stripper 69 is equal in i.d. to the stripper 16. Thesmaller stripper 34 is not shown since it has already been removed fromthe rotating sleeve.

In operation, the RBOP of the present invention is bolted to the top ofa well bore. Generally, it will be required that a blind ram bepositioned in underlying relationship respective to the RBOP. Further, anonrotating BOP 68 may be interposed between the RBOP and the blind ram.Sometime still other well control devices may be series connectedbetween the RBOP and the casing annulus.

The bowl clamp adapter ring 40 of the RBOP is affixed to the top of therotating sleeve by the illustrated bolts which are located in radiallyspaced counterbores so that the bolts are fairly spaced from thecoacting wedge surfaces 53, 54. The split rubber hold down plate usuallywill have previously been secured to the underlying metal flange of thestripper by the countersunk fasteners 27.

The clamp 43 is next operatively positioned on the apparatus to forcethe hold down plate towards member 54 by bringing the free ends 48, 49of the clamp towards one another as they pivot about support pin 45. Thenut on bolt 50 is torqued to a proper value, thereby closing wedgeinterface 53 and 54 and compressing the dovetail annular gasket 24within its annulus. The small stripper mount means is next positionedupon the large stripper mount means by making up fasteners 30. Wheredeemed desirable, a clamp similar to the arrangement disclosed at 43 canbe used in lieu of or in conjunction with the flange 37 so as to enablethe small stripper assembly to be rapidly removed from the largeassembly in the same before described manner.

The lub pump is started, and a finite continuous flow of lubricant flowsinto chamber 57 with excess lubricant exiting under the resilient seal60. Should a sudden increase in pressure be effected within the head,there can be no flow of debris into the seal assembly because of theforce provided by the low volumn positive dis placement pump, theincompressibility characteristics of the lubricant, and the design ofthe seal 60. The seal acts as a one-eay check valve with flow occurringinto the rotating head but not vice versa.

In making hole, the head rotates with the drilling string being loweredinto the well bore as may be required. During this time, the drillstring is in the configuration of FIG. 6 with wear occurring only onsmall stripper 34. The only time wear is effected upon rubber 16 is whena stabilizer or drill collar is passed therethrough. 1

When it is necessary to make a trip out of the hole, in accordance withthe embodiment of FIGS. 1-10, the drill pipe is withdrawn in the usualmanner until the larger o.d. portion 66 of the string sealingly engagesthe large stripper. With the collar being positioned in the illustratedmanner of FIG. 7, the small stripper assembly is removed from the largestripper mounting plate or hold down plate as diagrammaticallyillustrated in FIG. 8. The joint of drill pipe connected to the upperterminal end of the drill collar is removed, the small stripper assemblyis removed from the arm pipe, leaving the drill collar held securely inthe bowl of the turntable by conventional slips or the like, with thelower stripper controlling the well.

As seen in FIG. 9, the large stripper will deform sufficiently toconform to the contour of the stabilizer so as to enable it to bewithdrawn from the borehole. In order to prevent channeling of wellfluids through the rollers of the stabilizer, the blind ram or thehydrill located below the RBOP is closed about the drill collar, therebysealing off the annulus as the stabilizer is pulled through thestripper.

As seen in FIG. 10, the blind ram is opened and the drill collar is nextmoved up the borehole by raising the drill collar a maximum amount whichwill leave the stripper 16 engaged therewith, with the drill bit beinglocated between the blind ram and the BOP. The blind ram is againclosed, the drill collar and bit is moved in an upward direction untilit clears the turntable, whereupon the entire drill string is now out ofthe hole and can be prepared for the next trip into the borehole. Theblind ram is in control of the well during this part of the operation.

In the embodiment set forth in FIGS. 11-13, the drill pipe and uppermoststripper have already been removed from the assembly. The RBOP of thepresent invention is positioned above a fixed BOP 68 so that both thestrippers 16 and 69 are in control of the well while an enlargement 67is withdrawn from the borehole. This expedient enables circulation to beeffected through either of outflow lines 14 and 70 as may be requiredfor proper control of the well.

In FIG. 11, well fluid flows predominently through outlet 70, with asmaller flow occurring through the stabilizer and through the outlet 14,while stripper 16 controls the well. As seen in FIG. 17., after thestabilizer clears lowermost stripper 69 and is in the act of passingthrough the stripper 16, the well is controlled by the lowermoststripper 69. During this time, well fluid flows through outlet 70.

FIG. 13 shows the stabilizer clear of the RBOP with the lower outletbeing in control of the well. The drill collar can be lifted intounderlying; relationship respective to either of the strippers, theblind ram closed, and the bit pulled through the rubbers.

Going back into the hole calls for a reversal of the various aboveprocedures.

An important operative aspect of the invention lies in the split rubberhold down ring and its cooperative relationship with the clamp andstripper. This feature of the invention makes insitu replacement of thestripper possible by releasing the clamp and removing the split ring inan outward direction away from the string, and thereafter sliding thestripper up the string and through the rotory table, it being noted thatthe hold down plate is too large to be brought through the table. Hence,it is unnecessary to come out of the hole or to remove the RBOP in orderto replace the stripper. Further, the presence of bolts 27 is aconvenience rather than a necessity.

Still another important operative feature of the invention lies in theexternal venting arrangement of the hydraulic seal. Should the hydraulicseal commence to leak, debris will be vented externally and cannotpossibly contaminate the tapered roller bearings.

Further, advantage can be taken of the relative rotory motion effectedbetween the fixed and rotating sleeves for driving a lub pump for eachof the seal members. In particular, a pump affixed to the fixed sleevestructure can have its piston rod engaged with a lobe or cam located onthe rotating sleeve so that a finite quantity of lubricant is suppliedto the passageway 56 each revolution of the RBOP.

I claim:

1. A rotary drilling head assembly for well bore forming operationscomprising a stationary housing, a seal assembly supported by thestationary housing; said seal assembly comprising a rotatable sleevemember, a stationary sleeve member at least partially surrounding therotatable sleeve member so that a chamber is provided between saidstationary sleeve member and said rotatable sleeve member, bearing meansinterposed between said stationary sleeve member and said rotatablesleeve member and disposed within the chamber;

sealing means engaged with said rotatable sleeve member and saidstationary sleeve member for precluding leakage of fluid through saidchamber;

a stripper mount means, a first stripper means for receiving a marginallength of a drillstring therethrough; said first stripper means beingaffixed to said stripper mount means;

means by which said stripper mount means is removably affixed to theuppermost end portion of said rotatable sleeve;

a second stripper means superimposed above and in axial alignment withthe first recited stripper means; said first stripper means has a largerinside diameter relative to said second stripper means; and meansremovable mounting said second stripper means to said stripper mountmeans.

2. The apparatus of claim 1 wherein said seal means includes a chamberformed by spaced wall surfaces of said rotating sleeve member and saidstationary housing, spaced seal members in said chamber, each sealinglyengaging each of said spaced wall surfaces and isolating a portion ofsaid chamber which lies therebetween; an inlet passageway connected tothe isolated portion of said chamber; and, means by which a supply oflubrication is flow connected to said chamber.

3. The improvement of claim 2 wherein said spaced wall surfaces includea lower marginal interial inside peripheral wall surface of saidrotating sleeves and an upper marginal outer peripheral wall surface ofsaid stationary housing; a shoulder spaced from the terminal end of saidrotating sleeve member, a shoulder at the terminal end of saidstationary housing, the last two recited shoulders being spaced from oneanother; one said spaced seal member engaging each of the last tworecited shoulders with the shoulders being disposed in opposedrelationship.

4. The improvement of claim 1 wherein said means by which said strippermount means is removably affixed to the uppermost end portion of saidrotatable sleeve includes a clamp;

a bowl clamp adapter ring affixed to an upper end portion of saidrotatable sleeve member, a split rubber hold down plate overlying saidstripper, a wedge formed on the outer marginal edge portion of saidplate; an annular groove formed within said clamp, said groove having acomplimentary wedge surface for engagement with the wedge surface of theplate;

5. A rotary drilling head assembly as set claim 1 wherein:

said first stripper means comprises a ring member and a stripper rubber,said ring member being secured to the rotatable sleeve member, with saidstripper rubber being carried by the said ring member; a hold down plateoverlying said first stripper means;

and a clamp means having a wedge surface thereon which bears againstsaid hold down plate, and further including a shoulder formed on saidclamp means which engages said ring member to compress and seal thefirst stripper means to the rotatable sleeve member.

6. A rotary drilling head assembly for well bore forming operations,said head assembly having an axial chamber formed therethrough for thereception of a rotating driving member used in the drilling of wells,comprising:

a sleeve; a first housing adapted to concentrically receive said sleeve,thereby forming an annular chamber between said sleeve and said firsthousing;

bearing means disposed within said annular chamber such that said sleeveis rotatable;

a second housing, an outlet passageway for conducting fluid flow awayfrom said second housing; said first housing and said sleeve beingreceived by said second housing in a manner such that an annulus isformed between said sleeve and said second housing;

seal means positioned in said annulus; means for applying pressure onsaid seal means in a first direction thereby forming a rotatinghydraulic seal between said sleeve and said second housing;

stripper means, clamp means by which said stripper means is removablyaffixed to the upper extremity of said drilling head, said strippermeans being positioned to axially receive the driving membertherethrough, and further providing a seal preventing the egress of anywell fluids from within said second housing through the recited upperextremy;

said clamp means by which said stripper means is removably affixed tothe upper extremity of said drilling head further includes means bywhich a second relatively smaller stripper means may be affixed inoverlying relationship to said first stripper means so that a drillstring of different effective outside diforth in ameter can be sealinglyremoved from the borehole.

7. A drilling head according to claim 6 wherein said sleeve and saidsecond housing are spaced from one another to form a clearancetherebetween such that said sleeve is rotatable independently of saidsecond housing, so that leakage from said seal means positioned in saidannulus will be vented away from the bearing means.

8. A rotary drilling head assembly for wellbore forming operationscomprising a stationary housing, a seal assembly supported by thestationary housing; said seal assembly comprising a rotatable sleevemember, a stationary sleeve member at least partially surrounding therotatable sleeve so that a chamber is provided between said stationarysleeve member and said rotatable sleeve member, bearing means interposedbetween said stationary sleeve member and said rotatable sleeve memberand disposed within the chamber;

sealing means located between said rotatable sleeve member and saidhousing for precluding leakage of fluid therethrough; said sealing meansincludes a chamber formed by spaced wall surfaces of said rotatingsleeve member and said stationary housing, spaced seal members in thelast said chamber, each sealingly engaging each of said spaced wallsurfaces and isolating a portion of the last said chamber which liestherebetween; an inlet passageway connected to the isolated portion ofsaid chamber; and, means by which a supply oflubrication is flowconnected to the last said chamber;

a stripper mount means, a stripper means for receiving a marginal lengthof a drillstring therethrough; said stripper means being affixed to saidstripper mount means;

said rotatable sleeve member having means by which said stripper mountmeans is removably affixed to the uppermost end portion of saidrotatable sleeve member; and,

a second stripper means superimposed above and in axial alignment withthe first recited stripper means; said first stripper means has a largerinside diameter relative to said second stripper means means removablymounting said second stripper means to said stripper mount means.

9. A rotary drilling head assembly for wellbore forming operationscomprising a stationary housing, a seal assembly supported by thestationary housing; said seal assembly comprising a rotatable sleevemember, a stationary sleeve member at least partially surrounding therotatable sleeve so that a chamber is provided between said stationaryand rotatable sleeve members, bearing means interposed between saidstationary and rotatable sleeve members and disposed within the chamber;

sealing means located between said rotatable sleeve member and saidstationary housing for precluding leakage of fluid therefrom;

a stripper mount means, a first stripper means for receiving a marginallength of a drillstring theresaid stripper mount means;

means by which said stripper mount means is removably affixed to theuppermost end portion of said rotatable sleeve member comprising a ringmember secured to the rotatable sleeve member, with said first strippermeans being carried by said ring memher; a hold down plate overlyingsaid first stripper means; a clamp means having a wedge surface whichbears against said hold down plate, and a shoulder which engages saidring member to compress and seal the first stripper means to therotating sleeve member; and,

a second stripper means superimposed above and in axial alignment withthe first recited stripper means; means removably mounting said secondstripper means to said stripper mount means.

10. The apparatus of claim 9 wherein said first stripper means has alarger inside diameter relative to said second stripper means.

11. A rotary drilling head assembly for wellbore forming operationscomprising a stationary housing, a seal assembly supported by thestationary housing; said seal assembly comprising a rotatable sleevemember, a stationary sleeve member at least partially surrounding therotatable sleeve member so that a chamber is formed between saidstationary sleeve member and said rotatable sleeve member, bearing meansinterposed between said stationary sleeve member and said rotatablesleeve member and disposed within the chamber;

sealing means located between said rotatable sleeve member and saidstationary housing for precluding leakage of fluid through said chamber;

a stripper mount means, a stripper means for receiving a marginal lengthof a drillstring therethrough; said stripper means being affixed to saidstripper mount means;

said rotatable sleeve member having means by which said stripper mountmeans is removably affixed to the uppermost end portion of saidrotatable sleeve member;

a second stripper means superimposed above and in axial alignment withthe first recited stripper means; means removably mounting said secondstripper means to said stripper mount means;

said means by which said stripper mount means is removably affixed tothe uppermost end portion of said rotatable sleeve member includes aclamp;

a bowl clamp adapter ring affixed to an upper end portion of saidrotatable sleeve member, a hold down plate overlying said stripper, awedge formed on the outer marginal edge portion of said plate; anannular groove formed within said clamp, said groove having acomplimentary wedge surface for engagement with the wedge surface of theplate;

said clamp being made into two hinged together members which can bepivoted together to wedgedly engage said plate and which can be pivotedapart to release said plate.

12. The apparatus of claim 11 wherein said first stripper means has alarger inside diameter relative to said second stripper means.

1. A rotary drilling head assembly for well bore forming operationscomprising a stationary housing, a seal assembly supported by thestationary housing; said seal assembly comprising a rotatable sleevemember, a stationary sleeve member at least partially surrounding therotatable sleeve member so that a chamber is provided between saidstationary sleeve member and said rotatable sleeve member, bearing meansinterposed between said stationary sleeve member and said rotatablesleeve member and disposed within the chamber; sealing means engagedwith said rotatable sleeve member and said stationary sleeve member forprecluding leakage of fluid through said chamber; a stripper mountmeans, a first stripper means for receiving a marginal length of adrillstring therethrough; said first stripper means being affixed tosaid stripper mount means; means by which said stripper mount means isremovably affixed to the uppermost end portion of said rotatable sleeve;a second stripper means superimposed above and in axial alignment withthe first recited stripper means; said first stripper means has a largerinside diameter relative to said second stripper means; and meansremovable mounting saiD second stripper means to said stripper mountmeans.
 2. The apparatus of claim 1 wherein said seal means includes achamber formed by spaced wall surfaces of said rotating sleeve memberand said stationary housing, spaced seal members in said chamber, eachsealingly engaging each of said spaced wall surfaces and isolating aportion of said chamber which lies therebetween; an inlet passagewayconnected to the isolated portion of said chamber; and, means by which asupply of lubrication is flow connected to said chamber.
 3. Theimprovement of claim 2 wherein said spaced wall surfaces include a lowermarginal interial inside peripheral wall surface of said rotatingsleeves and an upper marginal outer peripheral wall surface of saidstationary housing; a shoulder spaced from the terminal end of saidrotating sleeve member, a shoulder at the terminal end of saidstationary housing, the last two recited shoulders being spaced from oneanother; one said spaced seal member engaging each of the last tworecited shoulders with the shoulders being disposed in opposedrelationship.
 4. The improvement of claim 1 wherein said means by whichsaid stripper mount means is removably affixed to the uppermost endportion of said rotatable sleeve includes a clamp; a bowl clamp adapterring affixed to an upper end portion of said rotatable sleeve member, asplit rubber hold down plate overlying said stripper, a wedge formed onthe outer marginal edge portion of said plate; an annular groove formedwithin said clamp, said groove having a complimentary wedge surface forengagement with the wedge surface of the plate;
 5. A rotary drillinghead assembly as set forth in claim 1 wherein: said first stripper meanscomprises a ring member and a stripper rubber, said ring member beingsecured to the rotatable sleeve member, with said stripper rubber beingcarried by the said ring member; a hold down plate overlying said firststripper means; and a clamp means having a wedge surface thereon whichbears against said hold down plate, and further including a shoulderformed on said clamp means which engages said ring member to compressand seal the first stripper means to the rotatable sleeve member.
 6. Arotary drilling head assembly for well bore forming operations, saidhead assembly having an axial chamber formed therethrough for thereception of a rotating driving member used in the drilling of wells,comprising: a sleeve; a first housing adapted to concentrically receivesaid sleeve, thereby forming an annular chamber between said sleeve andsaid first housing; bearing means disposed within said annular chambersuch that said sleeve is rotatable; a second housing, an outletpassageway for conducting fluid flow away from said second housing; saidfirst housing and said sleeve being received by said second housing in amanner such that an annulus is formed between said sleeve and saidsecond housing; seal means positioned in said annulus; means forapplying pressure on said seal means in a first direction therebyforming a rotating hydraulic seal between said sleeve and said secondhousing; stripper means, clamp means by which said stripper means isremovably affixed to the upper extremity of said drilling head, saidstripper means being positioned to axially receive the driving membertherethrough, and further providing a seal preventing the egress of anywell fluids from within said second housing through the recited upperextremity; said clamp means by which said stripper means is removablyaffixed to the upper extremity of said drilling head further includesmeans by which a second relatively smaller stripper means may be affixedin overlying relationship to said first stripper means so that a drillstring of different effective outside diameter can be sealingly removedfrom the borehole.
 7. A drilling head according to claim 6 wherein saidsleeve and said second housing are spaced from one another to form aclearance therebetween Such that said sleeve is rotatable independentlyof said second housing, so that leakage from said seal means positionedin said annulus will be vented away from the bearing means.
 8. A rotarydrilling head assembly for wellbore forming operations comprising astationary housing, a seal assembly supported by the stationary housing;said seal assembly comprising a rotatable sleeve member, a stationarysleeve member at least partially surrounding the rotatable sleeve sothat a chamber is provided between said stationary sleeve member andsaid rotatable sleeve member, bearing means interposed between saidstationary sleeve member and said rotatable sleeve member and disposedwithin the chamber; sealing means located between said rotatable sleevemember and said housing for precluding leakage of fluid therethrough;said sealing means includes a chamber formed by spaced wall surfaces ofsaid rotating sleeve member and said stationary housing, spaced sealmembers in the last said chamber, each sealingly engaging each of saidspaced wall surfaces and isolating a portion of the last said chamberwhich lies therebetween; an inlet passageway connected to the isolatedportion of said chamber; and, means by which a supply of lubrication isflow connected to the last said chamber; a stripper mount means, astripper means for receiving a marginal length of a drillstringtherethrough; said stripper means being affixed to said stripper mountmeans; said rotatable sleeve member having means by which said strippermount means is removably affixed to the uppermost end portion of saidrotatable sleeve member; and, a second stripper means superimposed aboveand in axial alignment with the first recited stripper means; said firststripper means has a larger inside diameter relative to said secondstripper means means removably mounting said second stripper means tosaid stripper mount means.
 9. A rotary drilling head assembly forwellbore forming operations comprising a stationary housing, a sealassembly supported by the stationary housing; said seal assemblycomprising a rotatable sleeve member, a stationary sleeve member atleast partially surrounding the rotatable sleeve so that a chamber isprovided between said stationary and rotatable sleeve members, bearingmeans interposed between said stationary and rotatable sleeve membersand disposed within the chamber; sealing means located between saidrotatable sleeve member and said stationary housing for precludingleakage of fluid therefrom; a stripper mount means, a first strippermeans for receiving a marginal length of a drillstring therethrough;said first stripper means being affixed to said stripper mount means;means by which said stripper mount means is removably affixed to theuppermost end portion of said rotatable sleeve member comprising a ringmember secured to the rotatable sleeve member, with said first strippermeans being carried by said ring member; a hold down plate overlyingsaid first stripper means; a clamp means having a wedge surface whichbears against said hold down plate, and a shoulder which engages saidring member to compress and seal the first stripper means to therotating sleeve member; and, a second stripper means superimposed aboveand in axial alignment with the first recited stripper means; meansremovably mounting said second stripper means to said stripper mountmeans.
 10. The apparatus of claim 9 wherein said first stripper meanshas a larger inside diameter relative to said second stripper means. 11.A rotary drilling head assembly for wellbore forming operationscomprising a stationary housing, a seal assembly supported by thestationary housing; said seal assembly comprising a rotatable sleevemember, a stationary sleeve member at least partially surrounding therotatable sleeve member so that a chamber is formed between saidstationary sleeve member and said rotatable sleeve member, bearing meansinterposed between said stationary sleeve member and sAid rotatablesleeve member and disposed within the chamber; sealing means locatedbetween said rotatable sleeve member and said stationary housing forprecluding leakage of fluid through said chamber; a stripper mountmeans, a stripper means for receiving a marginal length of a drillstringtherethrough; said stripper means being affixed to said stripper mountmeans; said rotatable sleeve member having means by which said strippermount means is removably affixed to the uppermost end portion of saidrotatable sleeve member; a second stripper means superimposed above andin axial alignment with the first recited stripper means; meansremovably mounting said second stripper means to said stripper mountmeans; said means by which said stripper mount means is removablyaffixed to the uppermost end portion of said rotatable sleeve memberincludes a clamp; a bowl clamp adapter ring affixed to an upper endportion of said rotatable sleeve member, a hold down plate overlyingsaid stripper, a wedge formed on the outer marginal edge portion of saidplate; an annular groove formed within said clamp, said groove having acomplimentary wedge surface for engagement with the wedge surface of theplate; said clamp being made into two hinged together members which canbe pivoted together to wedgedly engage said plate and which can bepivoted apart to release said plate.
 12. The apparatus of claim 11wherein said first stripper means has a larger inside diameter relativeto said second stripper means.